The present invention relates to a low-gloss dry-erase coating formulation. More specifically, the invention relates to an EB (electron beam) curable or UV (ultra violet) curable, low-gloss, dry-erase coating formulation. The invention further relates to methods of manufacturing the low-gloss dry-erase coating formulation.
Dry-erase boards also referred to as “whiteboards”, have become popular replacements to paper and chalkboards, as they are convenient, inexpensive, and versatile. Additionally, whiteboard surfaces can be combined with optical and electronic capabilities to produce surfaces from which the images can be reproduced, either on paper or digitally. Because of the capabilities that go far beyond those of traditional whiteboards, electronic whiteboards are also gaining popularity.
EB/UV-curable coatings are desirable for dry-erase surfaces as they are abrasion resistant and smooth. These EB/UV-curable coatings, however, produce high gloss surfaces. High gloss surfaces tend to create eyestrain and are difficult to see from certain angles. Thus, in many applications, low-gloss surfaces are desirable as they reduce eyestrain and can be viewed more easily from different angles.
The gloss in the coatings can be reduced by roughening the coating through the process of embossing or wrinkling. Gloss can also be reduced by introducing additives (i.e., matting agents such as silica). Surface roughening, however, may introduce sites that trap stains and inks and produce “ghosting”, i.e., a residual image of previously written material that remains after the writing is erased.
In addition, the gloss-reducing additives when added to the coating formulation tend to disperse imperfectly. Thus, dispersing equipment and dispersing agents, such as surface tension modifiers, are required for evenly dispersing these additives in the coating formulation.
In view of the aforementioned, it is desirable to minimize the use of both i.e., the surface roughening agents and the dispersing equipment and/or dispersing agents in the coating formulation.
It is further desirable to have an EB/UV curable, low-gloss, dry-erase coating formulation that are used to form hardcoats with minimal or preferably no “ghosting”.
Several patents disclose dry-erase compositions:
U.S. Pat. No. 6,476,965 (He et al.) discloses a dry erasable substrate and projection screen having a dry-erase low-gloss top layer, a pigmented layer, and a bead matrix layer comprising glass beads. The dry erasable top layer as disclosed in this invention, however, contains additives such as flatting agents that require dispersing agent and equipment to evenly disperse these additives. Further, it includes a pigmented layer and a bead matrix layer to form the low-gloss, dry-erasable article.
U.S. Patent Application No. 2004/0077497 (Korane et al.) discloses dry-erase surfaces produced from heat-cured resins. The dry-erase surfaces in this invention, however, use additives (e.g. flatting agents like amorphous precipitated silica) to reduce gloss. Thus, the composition disclosed in this application requires dispersing agents to evenly disperse the additives. Further, the reduced gloss, dry-erase surface as disclosed in this application is produced from heat-cured resins.
There is a need for an EB/UV-curable dry-erase coating formulation that has very low-gloss and yet minimizes the use of surface roughening agents, additives, dispersing equipment and/or dispersing agents.
There is a further need for EB/UV-curable low-gloss, dry-erase coating formulation that has enhanced dry-erase properties yet has superior writability (i.e., a marker is able to wet the dry-erase surface formed from the present coating formulation without dewetting or reticulation.)
There is a further need for EB/UV-curable low-gloss, dry-erase coating formulation that is capable of forming into a hard, abrasion and chemical resistant coating and yet is substantially flexible.